Various indole derivatives have been disclosed including those having a hydroxyl group at the 5-position, an alkoxycarbonyl group or a carboxyl group at the 2- and 3-positions and an alkyl group or an aryl group at the 1-position (Chem. Abst., 69, 2868n (1968); J. Prakt. Chem., 311(5), 807 (1969); and Chem. Abst., 70, 47295k (1969)) and having a hydroxyl group or a methoxy group at the 5-position, a 1-phenylethyl group at the 1-position and a methoxycarbonyl group at the 2- and 3-positions (Chem. Abst., 109, 92188n (1988)). Also disclosed are those indole derivatives having a bromine atom at the 6-position, a methyl group at the 1-position, a hydroxyl group or an acetoxy group at the 5-position, a hydrogen atom or an aminomethyl group at the 4-position, an ethoxycarbonyl group at the 3-position and a substituted or unsubstituted phenoxymethyl group at the 2-position (Chem. Abst., 115, 135866a ( 1991)).